Wireless ECG sensor system and method

ABSTRACT

A method of operating a wireless ECG sensor system may include (1) wirelessly transmitting, using a second antenna, electromagnetic radiation having a frequency equal to the resonant frequency of a first antenna of a sensor patch; (2) inductively receiving, using the first antenna, power for operating a passive RFID transponder of the sensor patch; and (3) operating the microcontroller of the sensor patch to perform at least one scan, wherein performing the at least one scan is defined as: (a) receiving a cardiac activity signal from at least one of the positive and negative electrodes of the sensor patch, (b) retrieving a location identifier from the storage medium of the sensor patch, and (c) operating the load modulation switch of the sensor patch to alter a voltage amplitude of the electromagnetic radiation to transmit to a demodulator a cardiac event reading comprising the cardiac activity signal and the location identifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/644,300 titled Wireless ECG Sensor System and Method and filed onMar. 11, 2015, now U.S. Pat. No. 10,098,544, the entire content of whichis incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to systems and methods relating towireless electrodes used to detect electrical signals from a subjectpatient.

BACKGROUND

Conventionally, electrodes are attached to a patient's skin and used fordetecting electrical impulses in a patient. These electrical impulsesmay be used, for example, to produce an electrocardiogram (ECG).

These conventional electrodes have wired connections extending from theelectrode a receiving device. The electrical signal received by theelectrode is sent along a wire and is then amplified and read by thereceiving device. Thus, while an ECG is being taken, the patient mustremain physically connected to the monitoring device.

The use of wired connections means that the electrode may becomeunplugged due to patient or other movement. Also, having wiredconnections tethers a patient to a particular piece of machinery,limiting patient mobility or requiring suspending detection using theelectrodes if the patient is moved away from the receiving device. Thiscan be an issue when transporting the patient, particularly intransition between an ambulance and a healthcare facility, or indeedwithin a healthcare facility.

There is also an issue with patient compliance wearing wired electrodes,as this causes discomfort and unease to the patient. A lack ofcompliance with electrode monitoring (e.g., disconnecting the wire fromthe electrode by the patient) means a break in monitoring and possibleerror or alert messages being sent to the medical staff. Accordingly,there is a need in the art for a solution for performing an ECG thataddresses the issues presented by requiring a wired connection.

This background information is provided to reveal information believedby the applicant to be of possible relevance to the present invention.No admission is necessarily intended, nor should be construed, that anyof the preceding information constitutes prior art against the presentinvention.

SUMMARY OF THE INVENTION

With the above in mind, embodiments of the present invention are relatedto wireless electrode systems and methods which may provide morereliable signal monitoring from an electrode and improved datacollection abilities.

An exemplary aspect of the invention is directed toward a wireless ECGsensor system including a sensor patch configured to attach to a userand an interrogator device separated from the sensor patch andconfigured to be carried by a housing. The sensor patch may include asubstrate having first and second sections and configured to exhibitdielectric dispersion between the first and the second sections. Thepositive electrode may be carried by the first section of the substrate,and a negative electrode may be carried by the second section of thesubstrate. The sensor patch may also include a passive radio-frequencyidentification (RFID) transponder carried by the substrate.

The RFID transponder may include a first antenna, a non-transitory andnon-volatile storage medium in electrical communication with the firstantenna, a load modulation switch in electrical communication with thefirst antenna, and a microcontroller in electrical communication withthe first antenna and in data communication with both the storage mediumand the load modulation switch.

The interrogator device may include a second antenna in electricalcommunication with a power source and configured to wirelessly transmitelectromagnetic radiation having a resonant frequency of the firstantenna of the sensor patch, and a demodulator configured to measure avoltage amplitude of the electromagnetic radiation wirelesslytransmitted by the second antenna.

The first antenna of the sensor patch may be configured to inductivelyreceive power for operating the passive RFID transponder of the sensorpatch from the electromagnetic radiation wirelessly transmitted by thesecond antenna of the interrogator device. Upon receipt of power, themicrocontroller of the sensor patch is configured to receive a cardiacactivity signal from at least one of the positive and negativeelectrodes of the sensor patch, to retrieve a location identifier fromthe storage medium of the sensor patch, and to operate the loadmodulation switch of the sensor patch to alter the voltage amplitude ofthe electromagnetic radiation to transmit to the demodulator a cardiacevent reading comprising the cardiac activity signal and the locationidentifier.

In some embodiments, the sensor patch may include an analog-to-digitalconverter carried by the substrate. In these embodiments, at least oneof the positive and negative electrodes may be configured to transmitthe cardiac activity signal in analog format to the analog-to-digitalconverter; and the analog-to-digital converter is configured to convertthe cardiac activity signal from analog format to digital format and totransmit the cardiac activity signal in digital format to themicrocontroller.

The sensor patch may also include an amplifier and an analog-to-digitalconverter both carried by the substrate. In some embodiments, at leastone of the positive and negative electrodes is configured to transmitthe cardiac activity signal in analog format to the amplifier. Theamplifier may be configured to amplify the cardiac activity signal to anamplified form to define an amplified cardiac activity signal, and totransmit the amplified cardiac activity signal to the analog-to-digitalconverter. The analog-to-digital converter may be configured to convertthe amplified cardiac activity signal from analog format to digitalformat and to transmit the amplified cardiac activity signal in digitalformat to the microcontroller.

The first antenna of the sensor patch may be configured to inductivelyreceive power from the electromagnetic radiation wirelessly transmittedby the second antenna of the interrogator device when the second antennais positioned a distance of less than one meter from the first antennaof the sensor patch.

The electromagnetic radiation wirelessly transmitted by the secondantenna may be characterized by a frequency selected from the groupconsisting of LF band (120-150 kHz) and HF band (13.56 MHz). The powersource comprises at least one of a battery and a power cable.

The power inductively received by the first antenna of the sensor patchmay be an AC input voltage. The RFID transponder of the sensor patch mayalso include at least one of a converter and a regulator, where theconverter is configured to convert the AC input voltage to a DC outputvoltage, and where the regulator is configured to sustain the DC outputvoltage within a target DC bias range.

The microcontroller of the sensor patch may also be configured to storethe cardiac activity signal on the storage medium of the sensor patch.

In some embodiments, the first antenna of the sensor patch may beconfigured to receive the location identifier from the electromagneticradiation wirelessly transmitted by the second antenna, and to store thelocation identifier on the storage medium. In addition, the sensor patchmay also be configured to receive a patch identifier from theelectromagnetic radiation wirelessly transmitted by the second antenna,and to store the patch identifier on the storage medium of the sensorpatch.

The interrogator device may include a communications link in datacommunication with the demodulator and with at least one of a wiredlocal area network (LAN) and a wireless LAN. The demodulator may beconfigured to transmit the cardiac event reading to a computing systemthrough the communications link. In some embodiments, the computingsystem may include a mobile phone. The computing system may beconfigured to detect an arrhythmia from the respective cardiac eventreadings transmitted by at least one of the plurality of sensor patches.

In some embodiments a plurality of sensor patches are used. The resonantfrequency of the first antenna of each of the plurality of sensorpatches may be configured to be distinct from the respective resonantfrequency of the first antenna of each of the other sensor patches, andthe interrogator device may be configured to wirelessly transmitelectromagnetic radiation having a plurality of transmission frequenciessuch that at least one of the plurality of the transmission frequenciesequals the respective resonant frequency of the first antenna of atleast one of the plurality of sensor patches.

In some embodiments, each of the plurality of sensor patches isconfigured to be positioned on the user according to an ECG electrodeplacement methodology selected from a group including standard 3-lead(Einthoven's Triangle), modified central lead (MCL1), standard 5-leadusing Lead V1, standard 5-lead using Lead V5, EASI™ 5-lead, andinterpolated 12-lead.

Some embodiments of the invention may include a remote monitoringsubsystem including a computing system having a processor for executinginstructions stored in a non-transitory computer readable memory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a patient and an ECG sensor systemaccording to an embodiment of the present invention.

FIG. 2 is diagram, from a top view, of an exemplary embodiment of theECG sensor of FIG. 1.

FIG. 3 is a side view of the ECG sensor of FIG. 1.

FIG. 4 is a diagram of an exemplary embodiment of the interrogator ofFIG. 1.

FIG. 5 illustrates an exemplary method associated with the ECG sensorsystem.

FIG. 6 is diagram, from a top view, of another exemplary embodiment ofthe ECG sensor of FIG. 1.

FIG. 7 is diagram of another exemplary embodiment of the interrogator ofFIG. 1.

FIG. 8 illustrates an exemplary computer system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Those ofordinary skill in the art realize that the following descriptions of theembodiments of the present invention are illustrative and are notintended to be limiting in any way. Other embodiments of the presentinvention will readily suggest themselves to such skilled persons havingthe benefit of this disclosure. Like numbers refer to like elementsthroughout.

Although the following detailed description contains many specifics forthe purposes of illustration, anyone of ordinary skill in the art willappreciate that many variations and alterations to the following detailsare within the scope of the invention. Accordingly, the followingembodiments of the invention are set forth without any loss ofgenerality to, and without imposing limitations upon, the claimedinvention.

In this detailed description of the present invention, a person skilledin the art should note that directional terms, such as “above,” “below,”“upper,” “lower,” and other like terms are used for the convenience ofthe reader in reference to the drawings. Also, a person skilled in theart should notice this description may contain other terminology toconvey position, orientation, and direction without departing from theprinciples of the present invention.

Furthermore, in this detailed description, a person skilled in the artshould note that quantitative qualifying terms such as “generally,”“substantially,” “mostly,” and other terms are used, in general, to meanthat the referred to object, characteristic, or quality constitutes amajority of the subject of the reference. The meaning of any of theseterms is dependent upon the context within which it is used, and themeaning may be expressly modified.

An embodiment of the invention text, as shown and described by thevarious figures and accompanying text, provides a wireless sensor systemwhich can be used to detect electrical impulses from a patient's body.For instance, the system may be used to gather information for anelectrocardiogram of the patient.

FIGS. 1-8 illustrate exemplary embodiments of wireless ECG sensors andrelated systems and methods.

As illustrated in FIG. 1, an exemplary embodiment of the inventionincludes an ECG sensor 110 and an interrogator device 250 separate fromthe ECG sensor 110. In use, the ECG sensor 110 may be attached to apatient 300.

The ECG sensor 110 may be powered by receiving a signal from theinterrogator device 250. The powered ECG sensor 110 may then detect anelectrical signal from the patient 300, and send information to theinterrogator device 250. The interrogator device 250 may then transmitthe information from the ECG sensor 110 to a monitoring system 400.

As illustrated in FIGS. 2 and 3, the ECG sensor 110 may include asubstrate 120 having a first section 122 and a second section 124 formedso as to exhibit a dielectric dispersion therebetween. First section 122may include a positive electrode 132 and the second section 124 mayinclude a negative electrode 134. The substrate 120 also includes aradio frequency identification device (RFID) 140. The RFID 140 may bedisposed between the positive electrode 132 and the negative electrode134 on a third section 126 of the substrate 120, or in any othersuitable location on the substrate 120. The substrate may be formed ofany desired material. In some embodiments, the substrate 120 will have alow electrical conductivity (e.g., plastic, fabric, etc.).

For example, as illustrated in FIG. 2, the electrodes 132 and 134 areseparated by a non-conductive portion of the substrate on which the RFID140 is formed (e.g., the third section 126). By so doing, a differencein potential can be detected between the electrodes 132 and 134.

It is noted that the substrate 120 may formed as a patch which can beadhered to a patient's body. Thus, the application of the ECG sensor 110to the patient may be done similarly to that of a conventional ECGsensor patch.

While the term RFID is used to describe an exemplary operation of acircuit used in the ECG sensor 110, the invention is not limited toconventional RFID chips. As illustrated in FIG. 2, the RFID 140 mayinclude an antenna 142 connected to a micro controller 148 and a loadmodulation switch 146. The micro-controller 148 may also be connected tothe load modulation switch 146, an external memory 144, and ananalog/digital controller (ADC) 170. The ADC(s) 170 may be connected tothe positive electrode 132 and the negative electrode 134.

The antenna 142 may be configured so as to resonate when a certainfrequency of electromagnetic signal is received. When the antenna 142receives the correct frequency, power is generated within the antenna142 and used to power microcontroller 148 and other components of ECGsensor 110. The structure of antenna 142 is not particularly limited andmay include, for example, a metal coil formed so as to resonate at aspecific frequency. The antenna 142 may inductively receive power as anAC signal. The antenna 142 may also include a power converter to convertthe power received to a DC signal. The antenna 142 may also include aregulator connected to the power converter so as to sustain the DCoutput voltage within a target DC bias range.

The microcontroller 148 may communicate with memory 144. The memory 144may be integral with the microcontroller 148 or may be external to themicrocontroller 148. The memory 144 may include software for themicrocontroller 148, and may also be used to store data collected fromthe electrodes 132 and 134, ECG sensor identification information,antenna signal reception timing information, location data, etc. Thememory 144 can be persistent (e.g., non-volatile), so as to retaininformation when power is not applied to the ECG sensor 110. Thus,memory 144 may be a non-volatile and non-transitory medium.

As noted above, the microcontroller 148 may also be connected, directlyor indirectly, to the electrodes 132 and 134. In some embodiments, themicrocontroller 148 is connected to one or more of the ADC 170, which isthen connected to the electrodes 132 and 134. The ADC 170 readsdifferences in the voltage across the electrodes 132 and 134 over timeand converts the detected analog signals to digital signals. Optionally,an amplifier 180 may also be included on the substrate 120. Theamplifier 180 may be located between one or both of the electrodes 132and 134 and the corresponding ADC(s) 170.

During normal operation, power is supplied to microcontroller 148 from asignal received by the antenna 142. As an electrical signal is picked upfrom the body through the electrodes 132 and 134 and converted by theADC 170, the electrical signal is sent to the microcontroller 148.

The detected ECG signal may then be transmitted by the antenna 142through the use of the load modulation switch 146 controlled by themicrocontroller 148. In addition, other information can also be sentthrough the antenna 142 through the use of the load modulation switch146. The other information which may be transmitted is not particularlylimited and may include identification information for the ECG sensor110, sample rate of the ECG data, etc. Indeed, memory 144 may be used tostore received location information (e.g., chest-left side), which maybe programmed in or received from the interrogator 250, so that thelocation information may be transmitted along with the identificationinformation of the ECG sensor 110. The information may be sentcontinuously or at intervals in a data packet.

FIG. 3 illustrates a simplified side view of an ECG sensor 110. As canbe seen in the Figure, the electrodes 132 and 134 may be located infirst section 122 and second section 124 of substrate 120, respectively.The first and second sections 122 and 124 are separated by a distance D.Distance D is large enough so that a dielectric dispersion is formedbetween the first section 122 and the second section 124, and inparticular between the electrodes 132 and 134. Thus, D is large enoughso that a potential difference may be detected between the electrodes132 and 134. Alternatively, the distance D may be calculated based onthe minimum distance between the electrodes 132 and 134, instead ofbased on the distance between the sections on which the electrodes arelocated.

FIG. 4 illustrates an embodiment of the interrogator device 250. Theinterrogator device 250 may be configured to both drive/power the ECGsensor 110 through the emission of an electromagnetic signal which isreceived by ECG sensor 110 through antenna 142, and to receive ECG andother data transmitted from the ECG sensor 110.

The interrogator device 250 may include a housing 210, an antenna 220connected to a power supply 224, a microcontroller 248, and ademodulator 230. The demodulator 230 and/or the microcontroller 248 mayalso be connected to a communications link, such as a wirelesstransmitter 240. The microcontroller 248 may be connected to and controlthe power supply 224, the demodulator 230 and the wireless transmitter240. While exemplary embodiments have been described using particularcomponents, the interrogator device 250 may be modified to have anycomponents which are able to transmit an electromagnetic signal to anECG sensor 110, receive an electromagnetic signal from the ECG sensor110, and store or pass-on the received data from the electromagneticsignal from the ECG sensor 110. Thus, any form of transmitter/receivermay be used in embodiments of the invention.

In one exemplary embodiment, the antenna 220 is driven so as to emit asignal at a certain frequency or frequencies which may power one or moreECG sensors 110. The antenna 220 is also configured to receive signalsfrom one or more of the ECG sensors 110.

The demodulator 230 reads the return signal(s) from the antenna 220. Thedemodulator 230 may also include a microprocessor to analyze and processthe information received by the antenna 220 or this may be done by themicrocontroller 248. One example may include reading the ECG sensor 110identification information and sending the ECG data identified asbelonging to a certain sensor to the wireless transmitter 240. Thewireless transmitter 240 may then send the information to the monitoringsystem 400. The method of sending the information to the monitoringsystem 400 is not particularly limited. For instance, the transmissionmay be done through a wireless network connection, Bluetooth, infrared,radio frequency, sonically, etc. The monitoring system 400 may be an ECGreader, a personal computer, a mobile phone, etc.

The monitoring system 400 may be configured to detect certain patternsin the ECG signals. For instance, the monitoring system 400 may beconfigured to detect an arrhythmia, a pulse rate, or any other cardiacor biological event which may be detected from the ECG signals.

The interrogator 250 may emit electromagnetic radiation to the ECGsensor 110 at any appropriate frequency. For instance, in someembodiments, the antenna 220 may be characterized by emitting afrequency selected from the LF band (120-150 kHz) and HF band (13.56MHz).

The power supply 224 may be a battery or some other energy storagedevice. It is also possible to utilize a power cord and external powerfor direct power and/or recharging the power supply 224.

While the ECG sensor 110 has been described as using a load modulationswitch 146, the invention is not limited to such an embodiment. One ofordinary skill in the art would understand that the signal may be sentusing other means such as amplitude modulation, frequency modulation,Wi-Fi protocols, etc.

By having the wireless ECG sensors 110 communicating with and beingpowered by the interrogator device 250, it allows the patient to bemonitored without being physically connected to any associatedmachinery. This may ease the performance of hospital procedures, makephysical activities more convenient for the patient, and increasecompliance with wearing ECG monitoring devices.

The distance at which the interrogator device 250 can power the ECGsensors 110 is not particularly limited and may be adjusted based on thesignal, power, possible interference, and other needs of the patientand/or health care provider. For instance, the interrogator 250 may beconfigured so as to transmit power to the ECG sensors 110 at a distanceof one or more meters away. Alternatively, the interrogator 250 may beconfigured to power the ECG sensors 110 at distances of less than sixinches away.

FIG. 5 illustrates an exemplary method of operation of the wireless ECGsystem. The method starts at block 500. At block 510, a signal isemitted from the interrogator device. The signal transmitted will besuch that it will cause a resonance in at least one ECG sensor antenna.At block 520, the ECG sensor receives the signal from the interrogatordevice which causes the antenna of the ECG sensor to resonate andgenerate power. At block 530, an electrical signal is detected by theelectrodes. This signal may be amplified and/or converted using an ADCprior to reaching the microcontroller. At block 540, the microcontrollercontrols the load modulation switch so as to vary the signal emitted bythe ECG sensor antenna, thereby transmitting information to theinterrogator device. At block 550, the interrogator receives thetransmission from the ECG sensor. At block 560, the demodulator extractsECG information, and any other embedded information, from thetransmission. At block 570, the ECG information and any other desiredinformation is transmitted to a monitoring device. The method ends atblock 580.

The method of use and application of the ECG sensors 110 is notparticularly limited and would be understood by one of ordinary skill inthe art. For instance, each of the plurality of sensor patches may bepositioned on the user according to an ECG electrode placementmethodology including but not limited to, the standard 3-lead(Einthoven's Triangle), the modified central lead (MCL1), the standard5-lead using Lead V1, the standard 5-lead using Lead V5, EASI™ 5-lead,and the interpolated 12-lead methodologies.

While some of the embodiments are described as the interrogator sendingand receiving signals to a single ECG sensor 110, this is done forsimplicity and the invention is not limited to such. For instance, theinterrogator may send signals on a plurality of frequencies wheredifferent frequencies resonate with different ECG sensors 110.Similarly, the return signal from the ECG sensors may be propagated ondifferent frequencies so that multiple sensors can differentiated. It isalso possible that all ECG sensors 110 may have antennas 142 tuned todifferent frequencies and the interrogator 250 emits signals atfrequencies for each of the ECG sensors 110. The interrogator mayinclude multiple antennas 220 which can emit a plurality of frequenciesat the same time, may have a single antenna emit multiple frequencies insequence, or some combination thereof.

In addition, in some embodiments, multiple ECG sensors 110 may beresonated/powered with a single frequency. The ECG sensors 110 may thenembed identification information in the control signal, or otherwisealter the signal, so that when the signals from the ECG sensors 110 arereceived by the interrogator 250 it can be differentiated which signalsare from which ECG sensor 110. This may be done by signal modulation,the first portion of the transmission may be ECG sensor information andthe second portion may be ECG signal data, or any other suitable meansas would be understood by one of ordinary skill in the art.

As illustrated in FIGS. 6 and 7, some embodiments of the invention mayinclude a power storage circuit 190′. Referring now to FIGS. 6 and 7,the power storage circuit 190′ and related elements will be discussed.All other elements are similar to those of FIGS. 1-5. Thus, likeelements will be labeled with a prime symbol (e.g., 250′) and will notbe discussed.

The inclusion of a power storage circuit 190′ in the ECG sensor 110′ mayallow the storage of information and power while the ECG sensor 110′ isnot being powered by the signal from the interrogator 250′. This mayallow a reduction in power consumption by reducing the scan rate of theinterrogator 250′. Generally, the minimum scan rate for an ECG is around868 MHz in order to detect heart rate and other information. However,other scan rates are possible depending on the signal analysis beingconducted.

During normal operation, the interrogator 250′ sends signals whichresonate with the antenna 142′ of a particular ECG sensor 110′ atregular or irregular intervals. These signals power the ECG sensor 110′and resonate in the antenna 142′ so as to transmit information back tothe interrogator 250′. At the same time, some of the power generated bythe antenna 142′ may be stored in a capacitor 150′. When the antenna142′ is not receiving a signal, and thus not generating power for theECG sensor 110′, the electrical signal detected by the electrodes 132′and 134′ can still be stored, for example in memory 144′, by using thepower stored in the power storage circuit 190′. When the ECG sensor 110′receives a signal from the interrogator 250′ again, it can transmit thestored signals and the currently detected signals. In some embodimentsthe signals may be time stamped, or otherwise ordered, when transmitted.In some embodiments, the data may be transmitted to the interrogator250′ in a first in first out system.

In some embodiments, the microcontroller 148′ may detect if thecapacitor 150′ has enough energy to send a transmission (e.g., activatethe load modulation switch 146′), continue monitoring the electrodes132′ and 134′, etc. If enough energy is not present, the microcontroller148′ may adjust its actions accordingly. For instance, if enough energyis not present to activate the load modulation switch 146′, then thedata may be saved to the memory 144′ and the load modulation switch 146′may not be activated at that time.

By having an ECG sensor 110′ which does not have to be constantlydriven/powered by the signal from the interrogator 250′, it may allowpower savings due to fewer signals being transmitted by the interrogator250′, and thus a longer battery life for the interrogator 250′. Theability of the ECG sensor 110′ being able to retain power may also beused so that the interrogator 250′ can send signals at differentfrequencies to different ECG sensors 110′ separately in sequence, inorder to reduce interference from other ECG sensors 110′ or make iteasier to identify which ECG sensor 110′ is sending the information tothe interrogator 250′.

Optionally, the capacitor 150′ may be replaced or augmented with arechargeable or non-rechargeable battery, or some other energy storagemechanism, so as to provide a longer or more reliable and persistentcharge.

In some embodiments, as shown in FIG. 7 and described above, theinterrogator 250′ may have multiple antennas 220′ which may each emitone or more different frequencies. Thus, the interrogator 250′ can powerand receive signals from multiple ECG sensors 110′ operating ondifferent frequencies at the same time. This can allow higher scan ratesthan would be possible by sending different frequencies sequentiallyfrom only one antenna 220′. The interrogator 250′ may have a differentantenna 220′ for each frequency, or may transmit multiple frequenciesover the same antenna 220′.

A skilled artisan will note that one or more of the aspects of thepresent invention may be performed on a computing device. The skilledartisan will also note that a computing device may be understood to beany device having a processor, memory unit, input, and output. This mayinclude, but is not intended to be limited to, cellular phones, smartphones, tablet computers, laptop computers, desktop computers, personaldigital assistants, etc. FIG. 8 illustrates a model computing device inthe form of a computer 810, which is capable of performing one or morecomputer-implemented steps in practicing the method aspects of thepresent invention. Components of the computer 810 may include, but arenot limited to, a processing unit 820, a system memory 830, and a systembus 821 that couples various system components including the systemmemory to the processing unit 820. The system bus 821 may be any ofseveral types of bus structures including a memory bus or memorycontroller, a peripheral bus, and a local bus using any of a variety ofbus architectures. By way of example, and not limitation, sucharchitectures include Industry Standard Architecture (ISA) bus, MicroChannel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI).

The computer 810 may also include a cryptographic unit 825. Briefly, thecryptographic unit 825 has a calculation function that may be used toverify digital signatures, calculate hashes, digitally sign hash values,and encrypt or decrypt data. The cryptographic unit 825 may also have aprotected memory for storing keys and other secret data. In otherembodiments, the functions of the cryptographic unit may be instantiatedin software and run via the operating system.

A computer 810 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby a computer 810 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may include computer storage mediaand communication media. Computer storage media includes volatile andnonvolatile, removable and non-removable media implemented in any methodor technology for storage of information such as computer readableinstructions, data structures, program modules or other data. Computerstorage media includes, but is not limited to, RAM, ROM, EEPROM, FLASHmemory or other memory technology, CD-ROM, digital versatile disks (DVD)or other optical disk storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canbe accessed by a computer 810. Communication media typically embodiescomputer readable instructions, data structures, program modules orother data in a modulated data signal such as a carrier wave or othertransport mechanism and includes any information delivery media. Theterm “modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia includes wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, radio frequency,infrared and other wireless media. Combinations of any of the aboveshould also be included within the scope of computer readable media.

The system memory 830 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 831and random access memory (RAM) 832. A basic input/output system 833(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 810, such as during start-up, istypically stored in ROM 831. RAM 832 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 820. By way of example, and notlimitation, FIG. 8 illustrates an operating system (OS) 834, applicationprograms 835, other program modules 836, and program data 837.

The computer 810 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 8 illustrates a hard disk drive 841 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 851that reads from or writes to a removable, nonvolatile magnetic disk 852,and an optical disk drive 855 that reads from or writes to a removable,nonvolatile optical disk 856 such as a CD ROM or other optical media.Other removable/non-removable, volatile/nonvolatile computer storagemedia that can be used in the exemplary operating environment include,but are not limited to, magnetic tape cassettes, flash memory cards,digital versatile disks, digital video tape, solid state RAM, solidstate ROM, and the like. The hard disk drive 841 is typically connectedto the system bus 821 through a non-removable memory interface such asinterface 840, and magnetic disk drive 851 and optical disk drive 855are typically connected to the system bus 821 by a removable memoryinterface, such as interface 850.

The drives, and their associated computer storage media discussed aboveand illustrated in FIG. 8, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 810. In FIG. 8, for example, hard disk drive 841 is illustratedas storing an OS 844, application programs 845, other program modules846, and program data 847. Note that these components can either be thesame as or different from OS 833, application programs 833, otherprogram modules 836, and program data 837. The OS 844, applicationprograms 845, other program modules 846, and program data 847 are givendifferent numbers here to illustrate that, at a minimum, they may bedifferent copies. A user may enter commands and information into thecomputer 810 through input devices such as a keyboard 862 and cursorcontrol device 861, commonly referred to as a mouse, trackball or touchpad. Other input devices (not shown) may include a microphone, joystick,game pad, satellite dish, scanner, or the like. These and other inputdevices are often connected to the processing unit 820 through a userinput interface 860 that is coupled to the system bus, but may beconnected by other interface and bus structures, such as a parallelport, game port or a universal serial bus (USB). A monitor 891 or othertype of display device is also connected to the system bus 821 via aninterface, such as a graphics controller 890. In addition to themonitor, computers may also include other peripheral output devices suchas speakers 897 and printer 896, which may be connected through anoutput peripheral interface 895.

The computer 810 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer880. The remote computer 880 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 810, although only a memory storage device 881 has beenillustrated in FIG. 8. The logical connections depicted in FIG. 8include a local area network (LAN) 871 and a wide area network (WAN)873, but may also include other networks 140. Such networkingenvironments are commonplace in offices, enterprise-wide computernetworks, intranets and the Internet.

When used in a LAN networking environment, the computer 810 is connectedto the LAN 871 through a network interface or adapter 870. When used ina WAN networking environment, the computer 810 typically includes amodem 872 or other means for establishing communications over the WAN873, such as the Internet. The modem 872, which may be internal orexternal, may be connected to the system bus 821 via the user inputinterface 860, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 810, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 8 illustrates remoteapplication programs 885 as residing on memory device 881.

The communications connections 870 and 872 allow the device tocommunicate with other devices. The communications connections 870 and872 are an example of communication media. The communication mediatypically embodies computer readable instructions, data structures,program modules or other data in a modulated data signal such as acarrier wave or other transport mechanism and includes any informationdelivery media. A “modulated data signal” may be a signal that has oneor more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Computer readable media may includeboth storage media and communication media.

Some of the illustrative aspects of the present invention may beadvantageous in solving the problems herein described and other problemsnot discussed which are discoverable by a skilled artisan.

While the above description contains much specificity, these should notbe construed as limitations on the scope of any embodiment, but asexemplifications of the presented embodiments thereof. Many otherramifications and variations are possible within the teachings of thevarious embodiments. While the invention has been described withreference to exemplary embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe invention. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from the essential scope thereof. Therefore, it isintended that the invention not be limited to the particular embodimentdisclosed as the best or only mode contemplated for carrying out thisinvention, but that the invention will include all embodiments fallingwithin the scope of the appended claims. Also, in the drawings and thedescription, there have been disclosed exemplary embodiments of theinvention and, although specific terms may have been employed, they areunless otherwise stated used in a generic and descriptive sense only andnot for purposes of limitation, the scope of the invention therefore notbeing so limited. Moreover, the use of the terms first, second, etc. donot denote any order or importance, but rather the terms first, second,etc. are used to distinguish one element from another. Furthermore, theuse of the terms a, an, etc. do not denote a limitation of quantity, butrather denote the presence of at least one of the referenced item.

Thus the scope of the invention should be determined by the appendedclaims and their legal equivalents, and not by the examples given.

That which is claimed is:
 1. A method of operating a wireless ECG sensorsystem wherein the wireless ECG sensor system comprises a sensor patchand an interrogator device, wherein the sensor patch comprises asubstrate, a positive electrode and a negative electrode carried by andpositioned in dielectric separation upon the substrate, and a passiveradio-frequency identification (RFID) transponder having a firstantenna, a non-transitory and non-volatile storage medium, a loadmodulation switch, and a microcontroller, and wherein the interrogatordevice comprises a demodulator and a second antenna, the methodcomprising: wirelessly transmitting, using the second antenna of theinterrogator device, electromagnetic radiation having a transmissionfrequency equal to a resonant frequency of the first antenna of thepassive RFID transponder; inductively receiving, using the first antennaof the passive RFID transponder, power for operating the passive RFIDtransponder of the sensor patch from the electromagnetic radiationwirelessly transmitted by the second antenna of the interrogator device;and upon receipt of power, operating the microcontroller of the passiveRFID transponder to perform at least one scan, wherein performing the atleast one scan is defined as: receiving a cardiac activity signal fromat least one of the positive and negative electrodes of the sensorpatch, retrieving a location identifier from the storage medium of thepassive RFID transponder, and operating the load modulation switch ofthe passive RFID transponder to alter a voltage amplitude of theelectromagnetic radiation received by the first antenna of the passiveRFID transponder to transmit to the demodulator a cardiac event readingcomprising the cardiac activity signal and the location identifier. 2.The method according to claim 1 wherein the sensor patch is adapted tobe attached to a user by positioning the sensor patch on the useraccording to an ECG electrode placement methodology selected from thegroup consisting of standard 3-lead (Einthoven's Triangle), modifiedcentral lead (MCL1), standard 5-lead using Lead V1, standard 5-leadusing Lead V5, and interpolated 12-lead.
 3. The method according toclaim 1 further comprising bringing the second antenna of theinterrogator device into a proximity of not more than one meter from thefirst antenna of the passive RFID transponder.
 4. The method accordingto claim 1 further comprising operating the microcontroller of thepassive RFID transponder to perform a plurality of scans in succession,wherein no two of the plurality of scans in succession occur at a scanrate of less than 868 MHz.
 5. The method according to claim 1 whereinthe sensor patch comprises a plurality of sensor patches each comprisinga passive RFID transponder, the resonant frequency of the first antennaof each of the passive RFID transponders being configured to be distinctfrom the respective resonant frequency of the first antenna of the otherpassive RFID transponders; the method further comprising the step ofwirelessly transmitting, using the second antenna of the interrogatordevice, electromagnetic radiation comprising a plurality of transmissionfrequencies such that at least one of the plurality of the transmissionfrequencies equals the respective resonant frequency of the firstantenna of the passive RFID transponder of at least one of the pluralityof sensor patches.
 6. The method according to claim 1 wherein theinterrogator device further comprises a communications link in datacommunication with the demodulator and with at least one of a wired LANand a wireless LAN; the method further comprising the step oftransmitting the cardiac event reading from the interrogator device to acomputing system through the communications link.
 7. The methodaccording to claim 6 further comprising the step of detecting, using thecomputing system, an arrhythmia from the cardiac event readingtransmitted by the interrogator device.